The primary function of Belzec was to exterminate Jews, while other camps also killed Roma and Sinti. During the camp's operation, from March 17, 1942 to June 28, 1943, an estimated 450,000 to 500,000 Jews, as well as a small number of Roma and Sinti, were murdered in its gas chambers.
The victims were initially transported by rail to Belzec from the ghettos in southern and eastern Poland and later on also from the Lvov and Stanislavov ghettos. On a typical day, as many as 12,000 Jews arrived in the camp, and nearly all were murdered the same day. The Belzec killing facilities were dismantled after the German troops crushed the Warsaw Ghetto Uprising in the spring of 1943. The Nazis then destroyed the evidence to conceal knowledge of the massacre.